Rozprawy doktorskie na temat „POM”

This study investigates translocation of particulate carbon and nitrogen from burned and unburned catchments within New Mexico's Valles Caldera National Preserve following severe wildfire. My research questions are: (1) how much carbon and nitrogen is eroded from burned slopes and re-deposited in debris fans? and (2) how do these quantities compare to fluvial export of particulate carbon and nitrogen from nearby unburned catchments? Results indicate that the ~200 kg ha⁻¹ of nitrogen per depositional area on the debris fans represents ~50 to 100 years' worth of atmospheric inputs. In total, 124 times more carbon and 21 times more nitrogen were deposited on the two fans than was exported in particulate form from all three unburned catchments combined in water year 2012. My findings suggest that post-fire erosion may increase nitrogen loading to downslope environments, with the potential to alter the biogeochemical budgets of both aquatic and terrestrial systems.

The design of traction mechanisms of continuous conveying units (e. g. plastic chains) is so far based on a purely mechanical dimensioning. However, mechanical limits are only applicable in a limited way to avoid system failure. With higher speeds or pressure, especially the thermal stress increases, which results in system failure based on softening or melting of the materials at a certain temperature. By means of systematic studies, correlations between friction temperature, coefficient of friction, wear and process parameters are examined. On this basis, a model for calculating the friction temperature is developed
Die Konstruktion von Zugmitteln für kontinuierliche Fördereinheiten (z. B. Kunststoffketten) beruht bisher auf einer rein mechanischen Dimensionierung. Allerdings sind mechanische Grenzwerte zur Vermeidung von Systemausfall nur bedingt anwendbar. Bei größeren Geschwindigkeiten oder Druck erhöht sich insbesondere die thermische Beanspruchung, was bei einer bestimmten Temperatur zum Systemausfall durch Erweichung oder Schmelzen der Werkstoffe führt. In systematischen Untersuchungen wurden die Korrelationen zwischen Reibungstemperatur, Reibungskoeffizient, Verschleiß und den Prozessparametern untersucht. Auf dieser Basis wurde ein Modell zur Berechnung der Reibungstemperatur entwickelt

Thesis (M.S. in Management) Naval Postgraduate School, December 1996.
Thesis advisor(s): Larry R. Jones, Jerry L. McCaffery. "December 1996." Includes bibliographical references (p. 103-106). Also available online.

La thèse présentée comporte deux parties. Une partie expérimentale qui consiste à étudier le caractère tridimensionnel de l'écoulement d'un PEbd dans des contractions brusques (planes et 3D). La cinématique de ce type d'écoulement a été mise en évidence par la technique du suivi des particules colorées. Dans les contractions planes, l'écoulement secondaire est caractérisé par un mouvement spiralé des particules dans la troisième direction, du plan de symétrie vers les parois latérales, avant de rejoindre l'écoulement principal en aval de la contraction. Avec les contractions purement 3D, le même type de cinématique a été observé : l'écoulement secondaire dans les vortex est orienté des plans de symétrie médians vers les plans de symétrie diagonaux, puis les particules rejoignent l'écoulement principal dans le chenal. La biréfringence induite par l'écoulement d'un PEbd dans une contraction plane confirme l'importance des effets 3D sur la distribution des contraintes globales. Ces effets sont détectés par la forme des franges isochromatiques en amont et en aval de la contraction. Dans les conditions 3D, ces franges ont une forme aplatie en amont avec l'apparition de franges en forme « W » en aval de la contraction, contrairement au cas 2D où nous avons observé une forme des franges en aile-papillon en amont de la contraction et l’absence de franges « W » en aval. Concernant l'origine de franges « W », notre étude montre que leur présence est corrélée avec la cinématique tri-dimensionnelle de ce type d'écoulement ; la possibilité de les observer dépend de la dimension de la géométrie dans la direction neutre. Dans la deuxième partie, une comparaison entre l’expérience et la simulation a été effectuée en terme de cinématique et de contraintes, ce qui constitue un critère de sélection important pour les modèles constitutifs. Les résultats obtenus confirment la pertinence du modèle Pom-Pom différentiel à prédire les écoulements du PEbd dans des géométries complexes, ainsi que l'importance d'une analyse 3D pour ce type d’études
The present PhD work contains two principal parts. The first part is dedicated to the experimental characterization of the 3D viscoelastic flow of LDPE in different contraction geometries. This study is focused on the global flow kinematics characterized in terms of experimental particle tracking and image analysis as well as on the stress distribution characterized in terms of flow induced birefringence. It was presented a detailed analysis of the complex three-dimensional motion of the secondary flow inside the vortex region. In contrary to the two-dimensional axisymmetric flow, where the secondary vortex motion is completely separated from the bulk flow, the detected 3D vortex was proven experimentally to be open with much more complex flow kinematics. In the case of 3D planar contraction flow the material is entering the vortex region at the plane of symmetry and gradually moving to the side wall where it goes to the slit die of the contraction. In the case of 3D square to square and square to circular contraction geometry, the material is entering the vortex region at the median planes and moves in helical manner to the diagonal planes of symmetry where it goes to the capillary die of the geometry. The flow induced birefringence confirms the 3D character of the stress distribution. The main character of the 3D viscoelastic stress distribution is expressed by the presence of more flatten type of fringes in the upstream part of the contraction as well as the appearance of specific “W” shaped fringes at the beginning of the downstream part. In fact our results give the first confirmation of the 3D nature of the “W” fringes. The second part presents an extensive comparison between the experimental results of part 1 and the 3D numerical simulations based on the recently proposed Pom Pom differential model. A good up to excellent agreement in terms of flow kinematics and stress distribution was observed. These encouraging results confirm the excellent predictive capabilities of the Pom Pom differential model as well as the necessity of full 3D numerical analysis for this kind of complex 3D flows

This PhD thesis investigated the incorporation of Polyhedral Oligomeric Silsesquioxanes (POSS) in thermoplastic base materials via melt-blending procedures. Particularly, a focus is taken on the enhancement of the thermal resistance through the addition of different types of POSS on two popular engineering plastics known by their low thermal stability, one being a semi-crystalline copolymer i.e. polyoxymethylene (POM) and the other an amorphous copolymer i.e. acrylonitrile butadiene styrene grafted with maleic anhydride (ABS-g-Ma). Different nanocomposites have been produced, from which its morphology, miscibility, structure, thermal properties and appearance behaviour before and during the thermoxidative degradation is herein quantified and discussed together with the resulting benefits and drawbacks. All the nanocomposites have been produced via melt-blending, using the nanofillers Glycidyl, Glycidyl-Isobutyl, Aminopropyl-isobutyl and Poly(ethylene-glycol) for the POM matrix, and Amino-Propyl Isobutyl, Glycidyl, and Trisilanol for the ABS-g-Ma matrix. The incorporation adequacy of the nanofillers into the matrix has been pre-assessed with the Hoy¿s solubility calculation method and later on corroborated with scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The quantification of the thermal degradation behaviour of each sample at different temperatures and exposure times was carried out through Fourier transform infrared spectrography (FTIR), thermogravimetric analysis (TGA) including the degradation kinetics and, ultimately, the sample appearance progress has been assessed in terms of yellowing by means of colour spectrophotometry (Cielab). The results showed that the presence of different POSS's used with the POM matrix improves dramatically the thermal stability of the base material and that such improvement is proportionate to the solubility compatibility between matrix and the nanofiller. The best performance was found with Aminopropyl-isobutyl, whereby the temperature of maximum rate of degradation (TMAX) increased by 22ºC. Said improvement is also seen in the conditions at which the nanocomposite developed only 2% of carbonyl yield and 8% of yellowing compared to the standard POM copolymer, which is taken as the base reference with 100% deterioration suffered in the above two indicators. However, the performance of the different nanocomposites produced in this work with ABS-g-Ma has not been as encouraging as the POM-based nanocomposites described above. Although the SEM morphological analysis show adequate incorporation and miscibility of the nanofillers into the matrix, the GPOSS and the TPOSS nanocomposites provided no relevant improvements in thermal stability when compared to the base ABS-g-Ma, and the APOSS blend exhibits a very slight decay in almost all the quantitative analysis carried out in this work.
Los avances producidos en años recientes en el campo de la nanotecnología y sus aplicaciones en los materiales están aportando grandes mejoras en el rendimiento de los mismos en áreas como la resistencia mecánica, estabilidad térmica, propiedades ópticas y eléctricas, entre otras. Por otro lado, el mundo de la ingeniería y el diseño de componentes plásticos está llevando los materiales cada vez más a su límite, con el fin de poder ofrecer el máximo rendimiento al mínimo coste. Esta realidad implica la necesidad creciente de customizar estructuras poliméricas con propiedades mejoradas en áreas específicas para cada aplicación. A pesar de los desarrollos que se han estado produciendo últimamente en nanocompuestos termoplásticos, el conocimiento en este campo es aún limitado, y requiere de más iniciativas de investigación y desarrollo sobre el amplio campo de posibilidades que nos ofrecen los nanocompuestos. El objetivo de esta tesis es contribuir en el conocimiento de los nanocompuestos a través del estudio de los efectos de varias nanocargas del tipo Polyhedral Oligomeric Silsesquioxanes (POSS) en el comportamiento de la resistencia térmica del copolímero semicristalino polióxido de metileno (POM) y del terpolímero amorfo acrilonitrilo‐butadieno‐estireno (ABS), los cuales son dos plásticos técnicos susceptibles a la termoxidación. Diferentes nanocompuestos se han elaborado con el fin de estudiar su morfología, miscibilidad, estructura, propiedades térmicas y apariencia, así como los beneficios y contrapartidas que resultan de ellos. Los nano‐compuestos han sido elaborados mediante el método de mezcla en estado fundido (melt‐blending), utilizando cuatro nano‐cargas distintas para el POM, siendo Glicidil, Glicidil‐Isobutil, Aminopropil‐isobutil y Poli(etilen‐glicol), y tres nano‐cargas para el ABS, siendo Amino‐Propil Isobutil, Glicidil y Trisilanol La compatibilidad teórica de las nano‐cargas se ha calculado mediante el método de solubilidad de “Hoy”, y se ha corroborado con microscopia electrónica de barrido (SEM) y calorimetría diferencial de barrido (DSC). Posteriormente, cada material base y sus distintas variantes de nano‐compuestos se han sometido a diferentes condiciones de termo‐oxidación en términos de temperatura y tiempo de exposición. El comportamiento a la degradación de cada muestra se ha cuantificado mediante los métodos de espectroscopia de infrarrojos por transformada de Fourier (FTIR), análisis de termogravimetría (TGA) incluyendo cinética de degradación, y finalmente mediante espectrofotometría (Cielab) para definir el progreso de la apariencia de la muestra en términos de amarilleamiento. Los resultados derivados de la inclusión de los diferentes POSS utilizados en la matriz de POM han mejorado sustancialmente la estabilidad térmica del mismo, y dicha mejora es proporcional a la compatibilidad de solubilidades entre el POM y los POSS utilizados. El mejor comportamiento se produce con la incorporación de la nanocarga aminopropilisobutil, con una temperatura de máxima degradación (TMAX) incrementada en 22 ºC sobre la TMAX del POM original tomado como referencia. Esta mejora se refleja también con una reducción muy notable en la formación grupos carbonilo y en el amarilleamiento sufrido en la superficie de la muestra, siendo un 2% y 8% respectivamente comparados con los resultados obtenidos con la muestra equivalente del material POM original. En referencia a los nanocompuestos basados en ABS‐g‐Ma, a pesar de la adecuada solubilidad teórica entre la matriz y las diferentes nano‐cargas, así como la buena miscibilidad obtenida en la elaboración de las muestras y evidenciada en el análisis morfológico SEM, no se han podido obtener mejoras en términos de estabilidad térmica. Concretamente, la adición de GPOSS y TPOSS no han aportado beneficios relevantes en las propiedades del nanocompuesto final, y la nanocarga APOSS ha incluso afectado negativamente a la matriz con una ligera caída de la resistencia térmica.
Els avenços produïts en els últims anys tant en el camp de la nanotecnología com en les seves aplicacions en els materials, està contribuint en la millora del rendiment dels mateixos en àeras com la resistència mecànica, l’estabilitat tèrmica, i les propietats òptiques i elèctriques entre d’altres. Per altra banda, el món de l’enginyería i el disseny de components plàstics està portant els materials cada vegada més al seu límit amb la finalitat de poder oferir el màxim rendiment al mínim cost, i això comporta una necessitat creixent de customitzar les estructura polimèriques amb propietats especificament millorades en àreas molt concretes en funció de l’aplicació requerida. A pesar del desenvolupament que s’ha estat produint últimament en l’àrea de nanocompostos plàstics, el coneixement en aquest camp és encara limitat, i requereix de més iniciatives d’investigació per cobrir el potencial que ofereix aquesta classe de materials, així com conèixer també les seves limitacions. L’objectiu d’aquesta tesi es el de contribuïr en l’enteniment dels nanocompostos plàstics a través de l’estudi dels efectes de vàries nanocàrregues del tipus Polyhedral Oligomeric Silsesquioxanes (POSS) en el comportament de la resistència tèrmica del poli(òxid de metilè) (POM) com a material semicristalí, i l’acrilonitril‐butadiè‐estirè (ABS) com a material amorf. Val a dir que la selecció d’aquests dos polímers tècnics ha estat en part motivada per la seva susceptibilitat inherent a la termodegradació. Diferents nanocompostos basats amb aquests materials s’han elaborat amb la finalitat d’estudiar la seva morfología, miscibilitat, estructura, propietats tèrmiques i aparença, així com els beneficis i contrapartides que resulten d’ells. La preparació dels nanocompostos ha sigut mitjançant el mètode de barreja en estat fos (melt‐blending), util.litzant quatre nano‐càrregues diferentes per el POM, siguent glicidil, glicidil‐Isobutil, aminopropil‐isobutil y poli(etilenè‐glicol), i tres nano‐càrregues per el ABS, siguent amino‐propil isobutil, glicidil i trisilanol. La compatibilitat teòrica de les nano‐càrregues s’ha calculat mitjançant el mètode de solubitat de “Hoy”, i s’ha corroborat amb microscopia electrònica d’escombrat (SEM) i calorimetría diferencial d’escombrat (DSC). Posteriorment s’ha sotmès cada material base i les seves diferents variants de nanocompostos a diferents condicions de termo‐oxidació en termes de temperatura i temps d’exposició. El comportament a la degradació de cada mostra s’ha quantificat mitjançant els mètodes d’espectroscopía d’infraroigs per transformada de Fourier (FTIR), anàlisis de termogravimetría (TGA) incloent cinemàtica de degradació, i finalment mitjançant espectrofotometría (Cielab) per a definir el progrés de l’aparença de la mostra en termes d’engroguiment. Els resultats han mostrat, per una banda, que la inclusió dels diferents POSS util.litzats en la matriu de POM ha millorat substancialment l’estabilitat tèrmica del mateix, i aquesta millora és proporcional a la compatibilitat entre les solubitats del POM i del POSS. El millor comportament s’ha produït amb l’adició de la nano‐càrrega d’aminopropilisobutil, amb una temperatura de màxima degradació (TMAX) millorada en 22ºC en relació a la obtinguida amb la matriu de POM. Aquesta millora també es reflexa amb una reducció molt notable en la formació de grups carbonil i en l’engroguiment sofert en la superfície de la mostra, siguent un 2% i 8% respectivament comparats amb els resultats obtinguts amb la mostra equivalent del material POM original. En contrast, els nanocompostos basats en ABS‐g‐Ma no han ofert millores en termes d’estabilitat tèrmica, a pesar d’una adequada solubitat teòrica entre la matriu i les diferents nano‐càrregues util.litzades, així com la bona miscibilitat obtinguda en l’elaboració de les mostres i posteriorment evidenciada en l’anàlisi morfològic SEM. Concretament l’adició de GPOSS i de TPOSS no han aportat beneficis en les propietats del nanocompostos final, i la nano‐càrrega APOSS ha afectat negativament a la matriu amb una lleuguera caiguda de la resistència tèrmica

Mestrado em Engenharia Química
Nesta dissertação pretendeu-se avaliar a atividade catalítica de polioxometalatos à base de vanádio (H4PMo11VO40 e H5PMo10V2O40), suportados em materiais híbridos de celulose-sílica (HCS-V e HCS-V2, respetivamente) para a oxidação de compostos orgânicos voláteis (COV) presentes no ar poluído. Além disso, também se sintetizou, caracterizou e testou um novo POM à base de ruténio α-SiW9Ru4), suportado em híbridos de celulose-sílica (HCS-Ru). A caracterização do HCS-Ru foi realizada por análise termogravimétrica (TGA), difração de raios-X (XRD), análise elementar, espectroscopia de infravermelho com transformadas de Fourier (FTIR) e por espectroscopia de refletância difusa. Desta análise foi possível concluir quanto à maior estabilidade térmica e menor cristalinidade do híbrido em comparação com a pasta celulósica de origem. Por outro lado, também foi possível confirmar a presença do polioxometalato e determinar a relação molar W/Ru no HCS-Ru. Os estudos de oxidação foram efetuados com ar poluído urbano, por amostragem direta ou em saco, passando o ar em tubos com HCS-POM (catalisador) em paralelo com tubos contendo o HCS (branco). A corrente efluente foi introduzida em tubos de adsorção, contendo resinas porosas Carbopack-B e Carbopack-C, pelo método de amostragem ativa. Os COV foram analisados num sistema constituído por um injetor de desadsorção térmica acoplado a um cromatógrafo de fase gasosa com detetor de ionização de chama (GC/FID). Os materiais HCS-V e HCS-V2 apresentam elevada atividade catalítica na oxidação de diferentes famílias de COV, mostrando-se o catalisador HCS-V mais eficaz que o catalisador HCS-V2. Também foi testado o efeito de alguns parâmetros que poderiam influenciar a atividade dos catalisadores, tais como a composição do ar (amostragem on-line ou em saco), a presença de água (trap com carbonato de potássio), o método de síntese dos catalisadores e a presença de ozono (trap com iodeto de potássio). O teste de atividade catalítica ao HCS-Ru permitiu confirmar a elevada atividade catalítica para a degradação de COV, revelando-se assim bastante promissor na sua utilização em catálise oxidativa.
The aim of the present work was to evaluate the catalytic activity of vanadium polyoxometalates (H4PMo11VO40 and H5PMo10V2O40), supported on cellulosesilica hybrid materials (HCS-V and HCS-V2, respectively) for the oxidation of volatile organic compounds (VOC) in polluted air. Furthermore, a new ruthenium catalyst α-SiW9Ru4), supported on cellulose-silica hybrid materials (HCS-Ru) was synthesized, characterized and tested. The characterization of HCS-Ru was done by thermogravimetric analysis (TGA), X-ray diffraction (XRD), elemental analysis, Fourier Transform Infrared Spectra (FTIR) and diffuse reflectance spectroscopy. These analyses revealed that hybrid materials have higher thermal stability and lower crystallinity than the corresponding cellulose material. Besides, the presence of polyoxometalate was confirmed and the molar ratio W/Ru in HCS-Ru was determined. The oxidation studies were carried out with polluted urban air by passing it through tubes with the HCS-POM (catalyst) and HCS (blank). The exit stream was introduced into adsorbent tubes with porous resins Carbopack B and Carbopack-C by the active sampling method. The VOC were analyzed in a system with a thermal desorption injector and gas chromatograph with flame ionization detector (GC/FID). The catalysts HCS-V and HCS-V2 have high activity for the oxidation of different families of VOC, being the catalyst HCS-V more effective than the HCS-V2. Parameters such as the composition of the sampled air (sample online or in bag), the presence of water (trap with potassium carbonate), the synthesis of the catalyst and the presence of ozone (trap with potassium iodide) were also studied. The catalytic activity test confirmed the high activity of HCS-Ru for the degradation of VOC, revealing this material as very promising for oxidative catalysis.

This dissertation works towards the larger objective of identifying and assessing the key features of molecular structure that lead to desired polymer processing performance with an ultimate goal of being able to tailor-make specific macromolecules that yield the desired processing response. A series of eight well-characterized, high-density polyethylene (HDPE) resins, with varying degrees of sparse long chain branching (LCB) content, is used to study the effect of both LCB content and distribution on the rheological and commercial processing response using the Pom-pom constitutive relationship. A flow instability known as ductile failure in extensional flow required the development a novel technique known as encapsulation in order to carry out shear-free rheological characterization. Ductile failure prevents the rheological measurement of transient stress growth at higher strains for certain strain-hardening materials. This reduces the accuracy of nonlinear parameters for constitutive equations fit from transient stress growth data, as well as their effectiveness in modeling extensionally driven processes such as film casting. An experimental technique to overcome ductile failure called encapsulation in which the material that undergoes ductile failure is surrounded by a resin that readily deforms homogeneously at higher strains is introduced. A simple parallel model is shown to calculate the viscosity of the core material. The effect of sparse long chain branching, LCB, on the film-casting process is analyzed at various drawdown ratios. A full rheological characterization in both shear and shear-free flows is also presented. At low drawdown ratios, the low-density polyethylenes, LDPE, exhibited the least degree of necking at distances less than the HDPE frostline. The sparsely-branched HDPE resins films had similar final film-widths that were larger than those of the linear HDPE. As the drawdown ratio was increased, film width profiles separated based on branching level. Small amounts of LCB were found to reduce the amount of necking at intermediate drawdown ratios. At higher drawdown ratios, the sparsely-branched HDPE resins of lower LCB had content film-widths that mimicked that of the linear HDPE, while the sparsely-branched HDPE resins of higher LCB content retained a larger film width. Molecular structural analysis via the Pom-pom constitutive model suggested that branching that was distributed across a larger range of backbone lengths serve to improve resistance to necking. As the drawdown ratio increased, the length of the backbones dominating the response decreased, so that the linear chains were controlling the necking behavior of the sparsely-branched resins of lower LCB content while remaining in branched regime for higher LCB content HDPEs. Other processing variables such as shear viscosity magnitude, extrudate swell, and non-isothermal processing conditions were eliminated as contributing factors to the differences in the film width profile. The effect of sparse long chain branching, LCB, on the shear step-strain relaxation modulus is analyzed using a series of eight well-characterized, high-density polyethylene (HDPE) resins. The motivation for this work is in assessing the ability of step-strain flows to provide specific information about a material's branching architecture. Fundamental to this goal is proving the validity of relaxation moduli data at times shorter than the onset of time-strain separability. Strains of 1% to 1250% are imposed on materials with LCB content ranging from zero to 3.33 LCB per 10,000 carbon atoms. All materials are observed to obey time-strain separation beyond some characteristic time, Ï k. The presence of LCB is observed to increase the value of Ï k relative to the linear resin. Furthermore, the amount of LCB content is seen to correlate positively with increasing Ï k. The behavior of the relaxation modulus at times shorter than Ï k is investigated by an analysis of the enhancement seen in the linear relaxation modulus, G0(t), as a function of strain and LCB content. This enhancement is seen to 1) increase with increasing strain in all resins, 2) be significantly larger in the sparsely-branched HDPE resins relative to the linear HDPE resin, and 3) increase in magnitude with increasing LCB content. The shape and smoothness of the damping function is investigated to rule out the presence of wall-slip and material rupture during testing. The finite rise time to impose the desired strain is carefully monitored and compared to the Rouse relaxation time of the linear HDPE resins studied. Sparse LCB is found to increase the magnitude of the relaxation modulus at short times relative to the linear resin. It is shown that these differences are due to variations in the material architecture, specifically LCB content, and not because of mechanical anomalies.
Ph. D.

Aquí hem aplicat el Princeton Ocean Model als embassaments de Sau i Boadella, situats a Catalunya, Espanya. Les simulacions s'han realitzat a l'estació d'estiu, quan la columna d'aigua està estratificada de forma contínua, i sota un règim de brisa amb velocitats de fins a 4 m/s. Basant-nos en aquestes simulacions hem analitzat el camp d'ones internes i comparat els resultats numèrics amb dades experimentals disponibles. El model reprodueix adequadament tots els modes observats en l'espectre de la velocitat i temperatura mesurades i ajuda a identificar els diferents modes. Les simulacions mostren la importància dels modes rotacionals en el camp d'ones internes dels embassaments estratificats. En el període estudiat, el radi de Rossby per l'embassament de Sau és de l'ordre de 100 m, que és varies vegades més petit que la amplitud de l'àrea lacustre de l'embassament, i el número de Rossby és de l'ordre de 0.1, corroborant la importancia de l'efecte de Coriolis.
We applied the Princeton Ocean Model to the Sau and Boadella reservoirs, located in Catalonia, Spain. Simulations were done for the summer season, when the water column is continuously stratified, and under a breeze regime with velocities of up to 4 m/s. Based on these simulations we analyzed the internal wave field and compared the numerical results with available field data. The model adequately reproduces all significant modes observed on the spectra of measured velocity and temperature and helps to identify the different modes. The simulations show the importance of rotational modes for the internal wave field of the stratified reservoirs. Under the studied wind regime, the Rossby radius for the Sau Reservoir is of the order of 100 m, that is, several times smaller than the amplitude of the lacustrine zone of the reservoir, and the Rossby number is of order of 0.1, which corroborates the importance of the Coriolis effect.

In this article the correlation between the average molar mass and the melt flow rate (MFR) is achieved. Based on the example of Polyoxymethylene (POM) it is shown that a high average molar mass is associated with a low MFR (high viscosity). On the basis of this dependency, the mechanical properties of static and dynamic tensile strength, elastic modulus, hardness and notched impact strength are investigated. It was found that the characteristic values of static tensile strength, elastic modulus and hard-ness increase with increasing MFR (decreasing viscosity). On the other hand the dynamic long-term properties and notched impact strengths decrease with increasing MFR
Im Beitrag wird der Zusammenhang zwischen der mittleren molaren Masse und des Schmelzfließindex (MFR) hergestellt. Dabei wird am Beispiel von Polyoxymethylen (POM) ersichtlich, dass eine hohe mittlere molare Masse mit einem geringen MFR (hochviskos) einhergeht. Basierend auf dieser Abhängigkeit werden die mechanischen Eigenschaften statische und dynamische Zugfestigkeit, E-Modul, Härte sowie Kerbschlagzähigkeit untersucht. Dabei konnte festgestellt werden, dass die Kenngrößen statische Zugfestigkeit, E-Modul und Härte mit steigendem MFR (abnehmende Viskosität) zunehmen. Die dynamischen Langzeiteigenschaften und Kerbschlagzähigkeiten sinken hingegen mit zunehmendem MFR

Polyoxometalates (POMs) are a rapidly growing class of metal-oxygen-cluster anions. The properties of POMs can be modified by altering the POMs chemical composition and structure. Due to low cost, commercial availability, and synthetic tractability POMs have found application in various fields of chemistry and technology. POMs are reusable and thermally stable to oxidative conditions, making them an attractive alternative to chlorine for the delignification of wood pulp. The research addressed in this dissertation deals with detailed kinetic and mechanistic studies of K₅[SiVW₁₁O₄₀]·12H₂O, a POM used in the delignification of wood pulp, oxidation of phenolic lignin model compounds and milled wood lignin (MWL). Results from lignin model studies suggest an overall second-order reaction rate; first order with respect to both POM and phenolic substrate. It was observed that electron-transfer from neutral phenols was slower than that from the corresponding phenoxide anions. Hammett studies revealed the reaction involved the formation of an electron-deficient radical intermediate where the rate-determining step is electron transfer from a neutral substrate. The structure of the substituted phenol, in terms of its electron donating/withdrawing character, along with the position of the substituent on the aromatic ring heavily influences the reaction rates. Increasing the number of ortho methoxyl groups dramatically increased the reaction rate, e.g. phenol < guaiacyl < syringyl model structures. The ortho methoxyl group(s) resonance stabilizes and delocalizes the forming phenoxyl radical intermediate. Similarly, the reaction rate of para-substituted guaiacyl and syringyl model compounds showed a dependence on the nature of the para-substituent; inductive or resonance conjugated electron withdrawing effects and inductive donating effects. The effect of POM oxidation on the chemical structure of a Lodgepole pine MWL is investigated. ¹³C nuclear magnetic resonance (NMR) spectroscopic data revealed an approximate 28% decrease in β-O-4 inter-unit linkages after POM treatment, the decrease in β-O-4 inter-unit linkages being accompanied by an increase in carbonyl content. These results suggest that POM oxidation involves side-chain (such as α-OH/β-O-4) oxidation. ¹³C NMR spectroscopy along with gel permeation chromatography revealed an increase in the degree of condensation which supports the idea that radical coupling is a major reaction pathway in this process.
Forestry, Faculty of
Graduate

Thesis (Ph. D.)--Joint Program in Oceanography, Massachusetts Institute of Technology/Woods Hole Oceanographic Institution, 1998.
Includes bibliographical references.
by Elizabeth C. Minor.
Ph.D.

With this research, we work towards the overall objective of customizing polymer molecules in terms of their molecular structure to optimize processing performance. The work includes analysis of the rheology in shear and shear-free flows for sparsely long-chain branched, LCB, polyethylene, PE, resins; determination of the consistency of the molecular based constitutive model, the pom-pom model; for these flows, and evaluation of the same PE resins in film-casting. As we progress towards molecular systems with defined molecular structural characteristics, we transition from a linear low density polyethylene, LLDPE, based series of PE resins to a high density polyethylene, HDPE, based series of PE resins, each with materials of varying degrees of sparse LCB. Evaluation of the shear step-strain rheology for the series of LLDPE-based PE resins allows for the assessment of any inadequacies associated with the step-strain experiments and the ability of the K-BKZ analog of the pom-pom constitutive model to predict step-strain rheological behavior. Finite rise time and wall slip are addressed to ensure the accuracy of the experimental step-strain measurements and eliminated as factors contributing to the stress relaxation moduli response. Analysis of the K-BKZ analog of the pom-pom constitutive model includes comparisons between experimental stress relaxation moduli and predictions from the model using pom-pom model parameters determined from extensional rheology. The results show inconsistencies in the model predictions, where the predictions fail to capture the short time behavior and accurately dampen at larger strains. Pom-pom model parameters are determined using the K-BKZ analog of the pom-pom constitutive model and fitting the stress relaxation moduli. These results are qualitatively consistent indicating that branching occurs on the longest backbone segments, but the values appear to be unrealistic with respect to the molecular theory. Analysis of film-width reduction or necking during film-casting for the series of LLDPE-based resins determines whether uniaxial extensional rheological characteristics, in particular strain-hardening, that are a result of LCB influence the film-necking properties. At the lowest drawdown ratio necking is observed to be reduced with increasing LCB, and thus strain-hardening characteristics. At the higher drawdown ratios it is observed that LCB no longer reduces necking and the curves merge to the results found for linear PE, except in the case of LDPE, which shows reduced necking at all drawdown ratios. Furthermore, comparisons of film necking are also made to separate the effects of molecular weight distribution, MWD, and LCB. The results indicate that both broadening the MWD and the addition of sparse LCB reduce the degree of necking observed. It is established that film necking is more significantly reduced by LCB than by broadening the MWD. Analysis of the uniaxial extensional and dynamic shear rheology with the pom-pom constitutive model reveals that a distribution of branches along shorter relaxation time modes is important in reducing necking at higher drawdown ratios. Factors such as shear viscosity effects, extrudate swell, and non-isothermal behavior were eliminated as contributing factors because of the similar shear viscosity curves, N1 curves, and activation energies among the sparsely LCB PE resins. The same experimental concepts have been extended to the series of HDPE-based resins, but the lack of adequate uniaxial extensional data prevents a thorough analysis with respect to uniaxial extensional characteristics. Regardless, in the context of step-strain rheology, the results were found to be similar with those of the LLDPE-based series of resins, where a distinctive shape at short times was observed for any of the PE resins possessing some level of LCB that was not apparent in the linear PE resins. Film-casting revealed similar results to those of the LLDPE-based materials as well, but a broader spectrum of drawdown ratios revealed greater insight into how the distribution of branching controls the film-casting response. At low drawdown ratios all materials exhibit the same necking behavior. At intermediate drawdown ratios separation occurs where the linear PE resins experiences the most drastic necking, the sparsely LCB PE resins show reduced necking, and the LDPE shows an even greater reduction in necking. Progression then to the higher drawdown ratios results in similar necking behavior for the linear and sparsely LCB PE resins and greatly reduced necking for the LDPE. These results support the idea that to reduce necking the backbone segments that dominate the film-casting behavior must contain some level of LCB.
Ph. D.

The gene designated Pom-1 is a new mouse gene identified in the region of the Gin-1 common proviral integration site. The origin of the Gin-1 region has been described elsewhere (Villemur et al., 1987). The novel Pom-1 gene is testis-specific and encodes two major RNA species of 1.0 and 1.2 kbp. Our data have revealed that there is no clear evidence to suggest that Pom-1 is involved in the tumorigenic pathway that resulted in the Gross Passage A Murine leukemia virus-induced thymomas. The pattern of expression of Pom-1 was studied by a time course Northern blot, the STAPUT cell separation technique and in situ hybridization. Analysis of mRNA from enriched populations of spermatogenic cells from adult testes and localization by in situ hybridization revealed that Pom-1 transcripts are most abundant in the round and elongated spermatids, although there is a weak expression in pachytene spermatocytes. Immunocytochemistry data have shown protein expression to be localized in the Golgi apparatus of pachytene spermatocytes (stages IX-XII), round spermatids (steps 5-8) and elongated spermatids (steps 9-15).
The Pom-1 gene is not homologous to any sequences present in the Genebank. Sequence analysis predicts a 6 kilodalton protein which is basic, lysine and arginine rich ($ sim$12%). It is also relatively rich in potential phosphoacceptor amino acids ($ sim$20%), mainly threonine and serine, several of which are located in phosphorylation consensus sequences. These results suggest a role for the novel Pom-1 gene in spermatogenesis.

O presente trabalho tem como objetivo estudar o efeito da carga normal aplicada, da velocidade de deslizamento, do acabamento superficial e do tipo de contra-corpo, na degradação dos materiais poliméricos POM e UHMWPE, resultante do contato deslizante contra corpos rígidos. Para tanto, foram realizados ensaios de desgaste em um tribômetro do tipo pino-contra-disco, com os pinos de materiais poliméricos e os discos de alumina e aço inoxidável. Nos ensaios de desgaste, utilizou-se 3 valores de carga, 3 velocidades de deslizamento e 3 níveis de acabamento superficial do contra-corpo. Para cada condição de ensaio, foram realizadas 3 repetições. Durante os ensaios, foram monitoradas a temperatura na interface dos materiais, a força de atrito e a posição vertical do pino. O deslocamento vertical do pino devido ao desgaste foi utilizado para a determinação da taxa de desgaste do polímero. A distância percorrida pelos pinos sobre o disco foi de 3.500 metros. Os ensaios foram realizados em ambiente com umidade relativa controlada em 50 ± 5 %. As análises por microscopia eletrônica de varredura das superfícies de desgaste dos pinos e dos discos indicaram a ocorrência de três tipos de mecanismos de desgaste: a abrasão, a fadiga e a transferência de filme (adesão). Para analisar o comportamento do desgaste mediante as influências estudadas, um parâmetro de severidade global (PVR/DD) é proposto. No parâmetro PVR/DD, considerou-se a relação entre um fator mecânico (condição de pressão e velocidade, PV), um fator topográfico (rugosidade do contra-corpo, R) e um fator térmico (difusividade térmica dos materiais em contato, DD). Verificou-se que os níveis de desgaste dos materiais poliméricos são influenciados pela condição de severidade global do contato; entretanto, o efeito preponderante foi devido ao tipo de material do contracorpo. Como foi observado que o deslocamento vertical ocorre devido não somente ao desgaste, mas também à fluência do polímero, à atuação de diferentes mecanismos de desgaste e ao fenômeno da fusão, os resultados de cada material de polímero estudado foram organizados na forma de mapas em função da severidade global, salientando as regiões de atuação de cada fenômeno.
The present investigation aims to study the degradation of polymeric materials resulting from the sliding contact against rigid bodies. The effect of some tribological influences, such as the applied load, the sliding velocity, the surface roughness and the counter-face material, were investigated. Experimental sliding wear tests were performed through a pin-on-disc tribometer, with the pins of polymeric material and the discs of alumina and stainless steel. The testing conditions of the wear tests encompassed three values of load (normal pressure) and three values of sliding velocity, or PV values, and three ranges of disc surface roughness. Three tests were performed in each condition. The interface temperature between the specimens, the friction force and the vertical position of the pin were monitored along the tests. The vertical displacement of the pin, resulting from the wear, was used for the determination of the polymer wear rate. The total sliding distance was of 3,500 meters. During the tests, the relative humidity of the environment was controlled to 50 ± 5 %. Analyses on the worn surfaces of pins and discs performed through scanning electronic microscopy indicated the occurrence of three wear mechanisms: abrasion (scratches), fatigue (waves) and adhesion (transfer film). In order to analyze the wear behavior of the polymer, a parameter of global severity of the contact (PVR/DD) was proposed. This parameter comprised a mechanical factor (the PV values), a topographic factor (the disc roughness) and a thermal factor (the thermal diffusivity of the materials in contact). It was possible to verify that the polymer wear depended on the level of global severity of the contact, where the major effect was due to the counterface material. It was also observed that the vertical displacement of the pin occurred not only due to the wear phenomena, but also due to the creep and the melting of the polymer, both depending on the testing condition. The creep and the melting phenomena were considered in the polymer degradation behavior, organizing the results of polymeric pin displacement in degradation maps, showing the boundaries of each observed phenomena, in function of the contact global severity.

Ø
The dissertation is presented on 252 content pages which has been framed in five chapters and two annexures while the title page opens into a list of abbreviations followed by a foreword on the work. The core theme of the research work is to validate the extended photocatalytic properties of porphyrin-POM materials in evolving from UV to visible light range of solar spectrum. Which describing additional modes for synthesis of hybrid materials (i) electrostatic multilayer’s comprising of Dawson , sandwich Dawson type and preyssler,s POM in combination with free base tetracationic porphyrin [H₂TPhN(Me)₃P⁴⁺] (ii) an easy method of synthesis of two dimers with a pyridinium spacer (abbreviated 4-H₂–Zn and 3-H₂–Zn) (iii) Langmuir Schafer approach for hybrid monolayer. The prepared photoactive thin layers have been characterized by UV-visible spectroscopy and fluorescence spectroscopy for optical properties. Cyclic voltammetry for electrochemistry and ionic permeability studies. Atomic force microscopy (AFM) for surface morphology and its role in physical mechanism of reduction process and shape of nanostructures obtained. Transmission electron microscopy (TEM) has been used to interpret size and shape of dendritic silver nanoparticles obtained as photoreduction product. Although ,the ultimate goal is the photoreduction of heavy metals (Cr(VI), Hg(II), Cd(II), Pb(II) ), reduction of a simpler system like Ag⁺ ion has been chosen as a model system due to single electron simpler oxidation reduction process. A novel application of photocurrent generation from these hybrid films has been demonstrated in the fifth chapter of the manuscript as an initial studies which has enhanced the significance of all previously fabricated systems upto by many folds .The foresaid development of photovoltaic application has paved the way for future studies to enhance the photocurrent yield further by tuning the electron donor-acceptor system. Both components porphyrin and POM can be tuned with different axial substituent’s and stereo chemical properties to achieve maximum yield of solar energy as well as diversified metal nanostructure for nanoelectronics, e.g. silver dendrites for sensor applications. At the end of the manuscript, three appendices describe successively the experimental techniques used to carry out this work, the Job method used to determine the stoichiometry and formation constants of complex electrostatic and coordination, and then finally the origin or Protocols for the synthesis of various compounds used

Methods to measure the concentration of freely dissolved PAHs in pore water have been developed and are based on the usage of passive samplers, in this case polyoxymethylene (POM). Spiked samples (containing PAHs with 4-5 rings, methylated PAHs with 2-5 rings and dibenzothiophenes in three different concentrations) were placed on an end-over-end shaker for 28 days, to obtain equilibrium between the amount of PAHs accumulated on the POM strips and the amount of PAHs freely dissolved in the water. Four samples (medium concentration) were removed from the shaker after 7 and 14 days, respectively, and after 28 days were 12 samples (low, medium and high concentrations) removed. The variance of the average log(KPOM) values obtained from medium concentration were statistically tested, and showed that the coefficients for all compounds did not differ significantly over time. The coefficient difference between the three concentrations for the methylated PAHs were greater amongst the more hydrophobic compounds; 7,12-Dimethylbenz(a)anthracene had log(KPOM) of 5.64, 2.77 and 3.71 (low, medium, high). The hydrophilic compounds had coefficients that were more similar in the three concentrations; 1,6-Dimethylnaphthalene had log(KPOM) of 3.80, 2.62, and 3.39 (low, medium, high). Previous studies have determined log(KPOM) for several PAHs, and merged log(KPOM) for alkylated isomeric PAHs. The coefficients from the lowest concentration of serval methylated PAHs and Benzo(e)pyrene were similar to log(KPOM) values obtained for those compounds in an earlier study. The accuracy of risk assessments of PAH contaminated areas will increase when analysing individual methylated PAHs and using individual KPOM values for methylated PAHs, as in this study, instead of merged coefficients.

Misturas de poliacetal (POM), polímero de engenharia com boas propriedades mecânicas, com poliuretano termoplástico (TPU), um polímero composto por uma fase rígida e outra flexível visam buscar alternativa de materiais a serem utilizadas em bandas externas de roldanas, visando a diminuição da emissão de ruído das roldanas quando utilizadas em sistema de movimentação de portas de armários, em contato com um trilho metálico. Neste trabalho foram avaliadas as propriedades mecânicas, físicas, térmicas e morfológica de misturas de POM/TPU nas proporções 100/0, 80/20, 70/30, 60/40, 50/50, 40/60 e 0/100 (m/m). As misturas foram preparadas em extrusora dupla rosca corrotante e após os corpos de prova foram injetados em injetora convencional. O aumento dos teores de TPU nas misturas promoveu o aumento da resistência ao impacto, à abrasão e diminuição na dureza do material. Houveram aumentos da temperatura de deflexão térmica das misturas com o aumento do teor de POM. Através da microscopia eletrônica de varredura (MEV) pode ser analisada uma mistura homogênea com partículas dispersas de TPU em formato de gotículas. A avaliação de emissão de ruído mostrou que com a diminuição do módulo de elasticidade, com o aumento da quantidade TPU na mistura, ocorre a redução da emissão de ruído do mesmo, esta redução fica evidente em frequências acima de 1kHz, ocorrendo uma redução da emissão de ruído de 2-5dB.
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Bolsa Desenvolvimento de Tecnologia e Inovação
Polyoxymethylene (POM), an engineering polymer with good mechanical properties, blended with thermoplastic polyurethane (TPU), a polymer composed by a flexible and a rigid phase, are an alternative of materials to be used in external bands of pulleys, aiming to reduce the noise emission of pulleys when used in system drive cabinets doors, occurring pulleys contact with a metallic rail. In this work, the mechanical, physical, thermal and morphological properties of POM/TPU blends were evaluated in the proportions of 100/0, 80/20, 70/30, 60/40, 50/50, 40/60 and 0/100 (w/w). The blends were prepared in a twin screw extruder and after the samples were injected in a conventional injector. The increase in the levels of TPU on the blends promoted a rise in the impact resistance, abrasion and a decrease in the material hardness. There was an increase in the deflection heat temperature of the blends with enhanced content of POM. Through scanning electron microscopy (SEM) was observed a blend with the presence of dispersed TPU particles. The noise emission showed that with the decrease in the modulus of elasticity of the polymer occurs a reduction of noise emission. This reduction is evident in frequencies above 1 kHz, causing 2-5dB reduction of noise emission.

This project analyses the impact in the mechanical properties of Polyoxymethylene (POM) of three different blends of biodiesels: B0 with 0% of Rapeseed Methyl-ester (RME), B20 with 20% of RME and B100 with 100% of RME. Polyoxymethylene specimens have been subjected to an accelerated aging during 1600 hours at 85ºC. This is the equivalent to 20 years of life time. In addition, a thermal oxidation in air at the same temperature has been performed to check the impact of the temperature in the final degradation.Three different methods have been performed to calculate the diffusion rate, however and one of them has been selected for its reliable results. The second Fick´s law have been chosen to model the diffusion. The diffusion rate has been calculated for the B20 and B100 blend due to the B0 blend has a non-constant diffusion rate. B20 shows also some divergence while B100 fits the Fickian behaviour.A Finite Different approximation method has been used to predict the concentration profiles of the diffusion process of B20 blend. They have been compared with the results of the IR Microscope, with a clear misalignment between the expected and the actual values.Tensile tests have been done in different stages of the test to check the stress-strain behaviour of the specimens for each aging type. The most relevant parameter of degradation is the Elongation At Break (EAB), which decrease considerably a cause of the embrittlement. A study of the real stress-strain has been also done to assure the real behaviour of the material.A fracture surface study through Scanning Electron Microscope (SEM) and Light Microscope has been done to assure the brittle behaviour with the aging and the changes in the structure of the material.The swelling behaviour has been also modelled, and the bases for a future FEM analysis have been exposed.

>Magister Scientiae - MSc
The motivation to determine H2O2 lies in the fact that this chemical species plays a crucial role in diverse fields of practise such as cosmetic, food, diagnostic, pharmaceutical, clinical and environmental protection industries. Several methods such as chromatography, colorimetry, titrimetry and spectrophotometry have been developed for its detection. However, these methods are known to manifest underlying disadvantages such as high cost, time consuming, instability and complicated immobilization procedures. In this present study an enzyme-less electrochemical sensor based on Ag-Fe2O3/POM/RGO nanocomposite (POM stands for polyoxometalate and RGO stands for reduced graphene oxide) was successfully synthesised via a hydrothermal method and a photochemical reduction method for the detection of hydrogen peroxide (H2O2).

L'étude présentée a pour objet, d'une part de déterminer la densité électronique précise dans un composé à propriétés optiques non linéaires : 3-methyl-4-nitropyridine n-oxyde (pom) et d'autre part de calculer les moments moléculaires de la distribution de charge et de les comparer au tenseurs de la polarisabilité linéaire et de l'hyperpolarisabilité non linéaire de la molécule. Les différentes méthodes utilisées sont en accord sur l'évaluation des charges nettes atomiques. L'orientation du moment dipolaire ainsi que le potentiel électrostatique créé autour de la molécule ont bien montré le caractère donneur du groupement n-oxyde et le caractère accepteur du groupement nitro. La comparaison du tenseur de la polarisabilité linéaire au tenseur du moment quadripolaire de la distribution de charges montre l'existence d'un lien étroit entre les composantes diagonales de ces tenseurs, et cela constitue donc une première confirmation des relations de robinson. La comparaison des composantes du moment octipolaire et celles du tenseur de l'hyperpolarisabilité témoigne également d'une dépendance directe entre ces deux grandeurs, cependant une différence de signe est observée pour certaines composantes, cette ambiguïté peut être probablement expliquée par le développement du profacteur apparaissant dans la relation de Robinson.

La croissance cristalline en gel de tetra methoxysilane (tmos) est tres favorable a l'elaboration de materiaux solubles mineraux ou organiques, tels que 3-methyl-4-nitropyridine-1-oxide (pom) et n-(4-nitrophenyl)-(l)-prolinol (npp), qui possedent en outre des proprietes optiques non-lineaires. La structure du gel permettant d'obtenir peu de defauts dans les cristaux, une correlation a ete realisee entre la qualite cristalline caracterisee par topographie aux rayons x et les performances optiques en generation du second harmonique

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Ciência e Engenharia de Materiais
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A abertura de mercado para as empresas de fabricação de bens e serviços tem permitido um grande crescimento na área de processamento de materiais, onde produtos fabricados em materiais termoplásticos tomaram o lugar dos fabricados em materiais metálicos, tanto para produtos acabados como também na confecção de ferramentais protótipos. Estas ferramentas confeccionadas em materiais como o Epóxi pelo processo de Estereolitografia SL vem sendo utilizadas para a confecção de produtos pelo processo de moldagem por injeção. Exemplos como Poli (óxido de metileno) - POM, Polipropileno e Poliamida tem sido utilizados em experimentos utilizando esta técnica. Neste trabalho foi estudado o comportamento das amostras de poli (óxido de metileno) POM copolímero injetadas em molde SL utilizando técnica de fabricação rápida, confeccionado em resina HUNTSMAN 5260 pelo processo de estereolitografia, comparado com amostras injetadas em molde confeccionado em material metálico usinado. O comportamento das amostras foi estudado através de ensaios mecânicos, térmicos e de micrografia. Os experimentos mostraram que não houveram alterações no comportamento térmico dos moldes utilizando-se altos níveis de compactação pelo uso da pressão de recalque na moldagem por injeção do POM copolímero, sendo que as amostras obtidas em molde SL obtiveram maior grau de cristalinidade, porém com baixa estabilidade dimensional. As propriedades mecânicas das amostras injetadas em molde SL se mostraram com características de um material rígido e frágil, com níveis superiores aos encontrados nos experimentos com amostras injetadas em molde de aço. Nas amostras injetadas em molde SL verificou-se a existência de grandes cristais formados pelo efeito de resfriamento.

Com a finalidade de estudar as perturbações médias sobre a Plataforma Continental Sudeste (PCSE) causadas pela passagem de uma frente fria durante o verão, obteve-se um estado básico médio de correntes. Esse campo médio foi obtido com o POM (Princeton Ocean Model) através de simulação diagnóstica, seguida por curta rodada prognostica. As correntes modeladas para o verão na Plataforma Continental Sudeste assemelharam-se em alguns aspectos a correntes obtidas em fundeios de correntógrafos realizados pela Diretoria de Hidrografia e Navegação (DHN), e pelo Instituto Oceanográfico da Universidade de São Paulo, durante os projetos Ciculação Oceânica na Região Oeste do Atlântico Sul (COROAS) e Dinâmica do Ecossistema de Plataforma da Região Oeste do Atlântico Sul (DEPROAS), validando os resultados do modelo Durante a passagem da frente fria as correntes invertem em cerca de seis a nove horas após a passagem do sistema frontal por cada região da PCSE. As etapas da subsidência costeira foram modeladas, ocorrendo transporte de deriva do vento em direção à costa, na camada superficial (0-10m), e transporte de compensação ao longo da coluna d\'água, havendo empilhamento de água na região costeira. A força de gradiente de pressão barotrópica desenvolvida implicou na formação e intensificação do jato costeiro em direção a menores latitudes. Durante esse estado transiente associado à passagem do sistema frontal, a Água Tropical aproxima-se da costa em nível sub-superficial, misturando-se com as águas da plataforma continental A porção da Plataforma Continental Sudeste localizada ao sul da Ilha de São Sebastião é a que responde com maior intensidade à passagem do sistema meteorológico frontal. Na direção transversal à costa, predomina o balanço geostrófico, o qual é intensificado durante a passagem da frente fria, enquanto que ao longo da costa as águas são desviadas do referido balanço pela tensão de cisalhamento do vento e pela aceleração local. Em Cananéia, ocorre a maior amplitude de variação do nível do mar, que pode estar associada a um mecanismo de ressonância entre os ventos do sistema frontal e Ondas de Plataforma Continental geradas pelo vento, uma vez que possuem velocidades de propagação próximas. A plataforma continental adquire vorticidade relativa ciclônica durante a passagem da frente fria.
In order to study the pertubations caused on the South Brazil Bigth (SBB) caused by the passage of a cold front during Summer, a mean basic state for currents was obtained using the POM (Princeton Ocean Model) through diagnostic simulation, followed by a short round prognostic. The mean currents modeled are in certain instancies similar to the currents measured by meter moorings deployed by the Directorate of Hydrography and Navigation (DHN), and by Oceanographic Institute of the University São Paulo during the Projects Oceanic Circulation in the Western South Atlantic (COROAS) and Dynamic of the Ecosystem of the Shelf of the Western South Atlantic Region (DEPROAS), validating results model. During the cold front passage, the currents invert six to nine hours after the passage of the frontal system through each region of the SBB. The stages of coastal subsidence were modeled, with coastward wind drift transport at superficial layer and offshore compensation transport throughout the water column, with piling of water in the coastal region. The strength of the barotropic pressure gradient developed caused the formation and intensification of a coastal jet. During this transient stage associated with the passage of the frontal system, the Tropical Water approaches the coast within sub-surface layer, mixing with continental shelf waters. The portion of SBB located to the South of São Sebastião Island is the portion which is most influenced by the passage of the frontal system. In a normal direction to the coast, the geostrophic balance predominates, being intensified during the passage of the cold front, while along the coast, the waters is diverted from this balance by the wind stress and by the local acceleration, which tend to have opposite signs. Near Cananéia, there is the highest sea level elevation, which may be associated with a mechanism of resonance between the winds of the frontal system and the Continental Shelf Waves generated by the wind, since they have the same speed of propagation. The continental shelf acquires cyclonic relative vorticity during the passage of the cold front.

Polyoxometalates (POMs), which are inorganic metal oxide cluster anions with discrete structures, have been extensively studied in recent years due to their large variety of applications such as medicine, biology, catalysis, material sciences and chemical analysis. Ruthenium polypyridyl complexes have been extensively studied for their applications as photosensitizers in solar energy conversion and photoelectronic materials. Recently, ruthenium heterocyclic ligand complex-based building blocks have been used for the synthesis of hybrid organic-inorganic solids through the self-assembly. We are interested in the synthesis of ruthenium polypyridyl complexes and polyoxometalate anions through different ways such as coordination bonds, hydrogen bonds and ionic bonds to form hybrid organic-inorganic solids. Here, we report four novel hybrid organicinorganic compounds, [Ru(2,2¡¦-bpy)3]2[SiW12O40] (1), [Ru(2,2¡¦- bpy)2(CH3CN)2]2[SiW12O40] (2), [Ru(2,2¡¦-bpy)3][W6O19] (3), and [Ru(2,2¡¦- bpy)3]2[Mo8O26]„ª5H2O (4) ), (2,2¡¦-bpy = 2,2¡¦-bipyridine). Compounds 1, 3, and 4 were synthesized under hydrothermal reaction methods and compound 2 was synthesized by room temperature solution method. These solids were characterized by elemental analysis, UV-vis spectroscopy, fluorescence spectroscopy, thermogravimetric analysis, IR spectroscopy, powder X-ray diffraction, and Single crystal X-ray diffraction. X-ray xii crystallographic study showed that the crystal structures of compounds 1, 2, 3 and 4 were constructed by Coulombic forces and supramolecular interactions. These molecular compounds were further connected and formed 3D structure through Cƒ{H„ª„ª„ªOPOM and other weak interactions. Spectroscopic studies demonstrated that electronic communication occurred between POMs and the sensitizers.

Thesis (Ph. D.)--University of Missouri-Columbia, 2005.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on October 18, 2007) Vita. Includes bibliographical references.

Cette thèse traite de dédoublement cinétique, de fonctionnalisation et d’utilisation de composés chiraux dérivés de polyoxométalates lacunaires de structure Dawson [α1-P2W17O61]10¬-. La première partie traite de l’utilisation de complexes organosolubles TBA5K[α1-Hf-P2W17O61] pour catalyser l’addition de nucléophiles comme des ethers d’énol ou des acétals de cétènes silylés mais également des pronucléophiles sur des hémiaminals. La seconde partie détaille l’étude sur la préparation et l’utilisation de trichlorostannanes énantiopures en vue du dédoublement cinétique des composés chiraux lacunaires [α1-P2W17O61]10-¬. La fonctionalisation diastéréosélective de derive chiraux organosoluble TBA7[α2-RSnP2W17O61] est également présentée. Le dernier chapitre décrit des hybrides chiraux POM-imidazolidinones dont la chiralité est uniquement apportée par le polyanion. Utilisé avec succès pour catalyser de manière énantiosélective des réactions de Diels Alder, ces composés sont les premiers POM de structure chirale a transféré la chiralité de manière aussi efficace vers des composés organiques
This manuscript deals with the kinetic resolution, the functionalization and the use of chiral lacunary Dawson α1-POM [α1-P2W17O61]10-¬. The first part deals with the racemic organo-soluble TBA5K[α1-Hf-P2W17O61] complex used to catalyze the nucleophilic addition of silyl enol ethers, ketene-acetals and activated methylene C-nucleophiles onto hemiaminals. The second part describes the synthesis of enantiopure trichlorostannane complexes as resolving agents for the kinetic resolution of chiral [α1-P2W17O61]10-¬. The diastereoselective functionalization of organosoluble chiral TBA7[α2-RSnP2W17O61] is also reported. The final chapter describes chiral POM imidazolidinones hybrids based on the known chiral α1-Dawson POM. Successfully applied as asymmetric catalysts in Diels-Alder reactions, these compounds are the first intrinsically chiral POM to efficiently transfer chirality to organic products

A proposta deste trabalho concentra-se na exploração estética de caráter ilustrativo, do livro de poesia A Bela Acordada da poetisa Adília Lopes. Parte-se, assim, de uma reflexão interpretativa sobre a autora e a sua obra, passando pela análise de alguns modelos simbólicos presentes na sua expressão poética, ponderando ainda nos novos paradigmas a que o novo milénio e a sua sociedade de imagem/consumo, conduzem. Nesse sentido, são exploradas e representadas possibilidades pictóricas que, num registo ilustrativo, se adequam ao mundo alegórico para o qual a autora nos remete em A Bela Acordada. Representações, que renascem dos contos de fadas e histórias de natureza fabular ou mítica, projetadas agora para uma sociedade contemporânea; ABSTRACT: The purpose of this work focus on the aesthetics exploration of the illustrative character of the poetry book The awaken Beauty, from the poetess Adília Lopes. It begins with an interpretative reflection about the author and its work, by analyzing some of its symbolic patterns, of hers poetic expression, considering also the new patterns, which the new millennium and its consumption society leads us to. In that kind of sense the pictorials possibilities are represented and explored, in an illustrative way, that adjusts to the allegoric world, for which the author sends us in The Awaken Beauty. Representations that are born again from the fairy tales and the mythical or fable stories, projected now for Contemporary Society.

Dissolved organic matter (DOM) is a complex mixture of organic compounds and represents the largest reservoirs of carbon (C) on earth. Particulate organic matter (POM) is another important carbon component in C cycling and controls a variety of biogeochemical processes. Estuaries, as important interfaces between land and ocean, play important roles in retaining and transforming such organic matter (OM) and serve as both sources and sinks of DOM and POM. There is a diverse array of both autochthonous and allochthonous OM sources in wetland/estuarine ecosystems. A comprehensive study on the sources, transformation and fate of OM in such ecosystems is essential in advancing our understanding of C cycling and better constraining the global C budget. In this work, DOM characteristics were investigated in different estuaries. Dissolved organic matter source strengths and dynamics were assessed in a seagrass-dominated subtropical estuarine lagoon. DOM dynamics controlled by hydrology and seagrass primary productivity were confirmed, and the primary source of DOM was quantified using the combination of excitation emission matrix fluorescence with parallel factor analysis (EEM-PARAFAC) and stable C isotope analysis. Seagrass can contribute up to 72% of the DOM in the study area. The spatial and temporal variation of DOM dynamics was also studied in a freshwated dominated estuary fringed with extensive salt marshes. The data showed that DOM was primarily derived from freshwater marshes and controlled by hydrology while salt marsh plants play a significant role in structuring the distribution patterns of DOM quality and quantity. The OM dynamics was also investigated in a mangrove-dominate estuary and a comparative study was conducted between the DOM and POM pools. The results revealed both similarity and dissimilarity in DOM and POM composition. The dynamics of both OM pools are largely uncoupled as a result of source differences. Fringe mangrove swamps are suggested to export similar amounts of DOM and POM and should be considered as an important source in coastal C budgets. Lastly, chemical characterizations were conducted on the featured fluorescence component in OM in an attempt to better understand the composition and origins of the specific PARAFAC component. The traditionally defined ‘protein-like’ fluorescence was found to contain both proteinaceous and phenolic compounds, suggesting that the application of this parameter as a proxy for amino acid content and bioavailability may be limited.

Polymer dispersed liquid crystal (PDLC) films, consisting of micro-sized domains of a liquid crystal dispersing in a polymer matrix, serve as the basis of a variety of high-efficiency electro-optical effects. The thermo-optical properties of the PDLCs were investigated in this thesis. The thermal properties and the morphologies of four low molar mass mesogens were studied by DSC and polarized optical microscope (POM). There were significant super cooling/heating effects on the first order phase transitions but not on the mesophase transitions. The structural effects on the transition temperature were investigated. Between the two 4-alkoxybenzoic acids mesogens, the clearing temperature of 4-(octyloxy)benzoic acid was higher than 4-(decyloxy)benzoic acid because of the increasing chain length. Trans-4-methoxycinnamic acid had the highest melting temperature among the four mesogens despite the molar mass because the carboxylic acid termini of trans-4-methoxycinnamic acid gave rise to strong intermolecular attractions. The smectic phases of 4-(octyloxy)benzoic acid were classified as head-to-head bilayer orientational smectic structures, SmA2 and SmC2, respectively, by wide angle X-ray diffraction through measuring the d spacing of the liquid crystal. The total solubility parameter was used to evaluate matching a polymer-LC-solvent combination. PDLC films were prepared by the solvent induced phase separation method and suitable morphologies were achieved by thermal induced phase separation. The phase transition temperatures of PDLCs were shifted to a lower temperature due to the polymer dispersion effects. Different mesophases were observed in PDLC films when LC exhibited different mesophases. The LC fractions in the droplets were calculated from the nematic to isotropic enthalpies through the Smith equation. Two factors, thermal cooling rate and the LC concentration, which affect the size of the droplet dispersed in the polymer matrix, were investigated in the PVC dispersed 4,4'-azoxyanisole. The phase transitions of pHEMA dispersed 4-(octyloxy)benzoic acid and PVC dispersed 4,4'-azoxyanisole were investigated by TMDSC and quasi-isothermal TMDSC. The TMDSC results were analysed by the two approaches, reversing and non-reversing heat flow and complex heat capacity. The results of the phase transitions of the two PDLCs illustrated that in the PDLCs it involved both non-reversing, melting, and reversing, clearing and the transition between two mesophases. In the non-reversing transition, the transition temperature would be affected by super cooling/heating and the results obtained in the experiments were dependent on the experimental conditions, such as the heating or cooling rate, sample size and purge gas flow rate. However, in the reversing transition process, there were no super cooling/heating effects observed and it seemed that the experimental conditions were not so critical. Results could be monitored by Lissajous figures obtained from the quasi-isothermal TMDSC. The plots of modulated heat flow versus the derivative of modulated temperature can be used to alert to unfavorable experimental conditions where loss of system linearity could be seen.

International Telemetering Conference Proceedings / October 30-November 02, 1989 / Town & Country Hotel & Convention Center, San Diego, California
Verifying the quality of a PCM (or PAM) telemetry system is an important concern before any launch. A frame simulator generated test is definitely inchoate to exercise the link’s real world disturbances response behavior. It should be completed with tests involving some disturbances measurements.

Project management offices are expected to assist organisations in the successful delivery of projects portfolios, but often fail to meet expectations. This study contributes to the academic and practitioner understanding of project and portfolio success by providing a detailed insight into the factors and processes that drive the evolution of project management offices using routines as the unit of analysis. Project management offices are assumed to be the agent of change and strategy implementation; so, the organizational leaders need to understand the organizational context and how a successful PMO re-shape itself over time to increase its value to the organisation.

In this study, annual variations in biochemical composition of seston and zooplankton community were investigated to characterize the nutritional environment of zooplankton in the Mersin Bay, NE Mediterranean Sea. For this goal, seawater and zooplankton samples were collected at monthly intervals from two stations
one representing coastal and other representing open waters characteristics from November 2004 to January 2006. Seawater samples were collected with Niskin bottles from the sea surface. Zooplankton samples were collected both in the horizontal and vertical plane by towing a Nansen net (70 cm mouth diameter with 112 µ
m mesh). Surface seston chl-a, lipid, protein and carbohydrate concentrations were measured by fractionating seawater into three different size groups, 0.7-2.7, 2.7-18 and >
18 µ
m representing pico, nano and micro particulates in the seston. Zooplankton biomass and abundance were determined at four size fractions: 112-200, 200-500, 500-1000 and >
1000 µ
m
dry and organic weights were measured by gravimetric method and major taxonomic groups of zooplankton was identified under stereo-microscope. The nearshore station was always more productive than the offshore station in terms of chl-a, particulate organic matter (POM: protein+lipid+carbohydrate), zooplankton abundance and biomass. Chl-a maxima occured in spring and autumn at both stations. Very low chl-a concentrations at the offshore station (0.02-0.35 µ
g L-1) confirmed oligotrophic character of the Northeastern Mediterranean. The highest chl-a concentration (2.4 µ
g L-1) was observed in March 2005 at the nearshore station due to the input of Lamas River nearby. POM varied from 42.1 µ
g L-1 (in January 2006) to 1082 µ
g L-1 (in March 2005) and 53.7 µ
g L-1 (in January 2006) to 246 µ
g L-1 (in May 2005) at the nearshore and offshore stations, respectively. The oligotrophy of this system was indicated by the extremely low particulate lipid, protein and carbohydrate concentrations (1-3 times lower than in more productive systems). The most evident characteristic of this oligotrophic environment was the dominance of pico-POM throughout the study period, accounting for 31&ndash
65 % of the total carbohydrates, proteins, lipids and chl-a. The prt:cho ratio was generally lower than 1 (low in organic nitrogen). Carbohydrate was the dominant biochemical component at both stations. Zooplankton varied during the sampling period, and they showed two peak abundances, in spring and autumn, with small increase in summer. The higher biomasses of zooplankton were observed in summer and autumn in the entire water column, but in spring and autumn periods in the surface water. Zooplankton data showed that 200-500 and 112-200 µ
m size fractions were dominant in abundance at both stations. However, 200-500 µ
m size fraction was dominant in zooplankton biomass at nearshore, whereas >
1000 µ
m size fraction was at offshore station. Copepods were the most abundant zooplankton group and dominated the distribution of total zooplankton, followed by crustace nauplii, appendicularia, cladocera and pteropoda.